This invention relates to an electrophotographic photoreceptor, and an image forming apparatus and a processing cartridge each using the photoreceptor.
Recently, the main stream of technology of the electrophotographic photoreceptor is shifted to organic photoreceptor and the organic receptors using various kinds of materials are developed. Among them, the photoreceptor having a charge generation layer and a charge transportation layer piled with each other widely used, in such the photoreceptor different materials are each charged with the functions of the charge generation and the charge transportation.
The latent image formation method in the electrophotographic process can be roughly classified into an analogical image forming method in which a halogen lump is used as the light source and the reflected light from an original image is focused on the photoreceptor, and a digital image forming method in which digital electric signals corresponding to the original image are converted to light signals by a LED or laser and the light signals are focused on the photoreceptor. Recently, the digital latent image forming method is rapidly spread for a hard copy printer of personal computer or an ordinal copy machine according to the facility of such the method in the image treatment and application for a complex copy machine.
In almost original images, the area of the image portion is smaller than that of the non-image area. Consequently, a reverse developing process for developing the exposed area is mainly used for the writing by the digital method. It has been known as a peculiar problem of the image forming method using the reversal development that fog is formed by adhering the toner to the portion to be a white background of the image or formation of a black spot caused by a local defect of the photoreceptor. Such the problem is caused by a phenomenon that the potential of the photoreceptor surface which should be charged at a high potential in the reversal development of the digital image is locally dropped by leakage. Such the problem tends to be appeared accompanied with the recently improvement of the quality resolution of the image by which a defect of the latent image having a micron order size can be developed.
Technology using an interlayer is developed to solve such the problem. For example, an electrophotographic photoreceptor is known in which an interlayer comprising a resin and a titanium oxide particle dispersed in the resin is provided between an electroconductive substrate and the photosensitive layer. An interlayer containing a surface-treated titanium oxide particle is also known. Examples of such the surface-treated titanium oxide include titanium oxide surface-treated by iron oxide or tungsten oxide described in Japanese Patent Publication Open to Public Inspection, hereinafter referred to as JP O.P.I., No. 4-303846, titanium oxide treated by an amino group-containing coupling agent described in JP O.P.I. No. 9-96916, titanium oxide surface-treated by an organic silicon compound described in JP O.P.I. No. 9-258469 and titanium oxide surface-treated by a methylhydrogenpolysiloxane described in JP O.P.I. No. 8-328283. However, the formation of black spot cannot be sufficiently inhibited under a serious condition such as a high temperature and high moisture or a low temperature and low moisture even when the foregoing technology is applied. Moreover, problems such that a sufficient density cannot be obtained as a result of increase in the remained potential and the potential at the light-exposed area caused by repeating of the use are raised in such the case. JP O.P.I. No. 11-344826 proposes a photoreceptor having an interlayer using a branch-shaped titanium oxide surface-treated by a metal oxide or an organic compound. However, it is found according to the result of the examination based of the example described in the publication that the black spot preventing effect under the high temperature and high moisture condition is insufficient.
The object of the invention is to provide an electrophotographic photoreceptor forming no image defect such as the black spot. In detail, the object of the invention is to provide an electrophotographic photoreceptor having an interlayer by which formation of the image defect such as the black spot can be prevented, and an image forming apparatus using such the photoreceptor and a processing cartridge.
1. An electrophotographic photoreceptor having an interlayer provided between an electroconductive substrate and a photosensitive layer in which the interlayer contains a particle and has a light absorbance of not more than 0.25 per micrometer of thickness at a wavelength of 1,000 nm.
2. The electrophotographic photoreceptor described in 1 in which the particle is a metal oxide particle having a number average primary particle diameter of from 10 nm to 200 nm.
3. The electrophotographic photoreceptor described in the foregoing 2 in which the metal oxide particle is an N-type semiconductive particle.
4. The electrophotographic photoreceptor described in the foregoing 3 in which the N-type semiconductive particle is a titanium oxide particle.
5. The electrophotographic photoreceptor described in the foregoing 4 in which the titanium oxide particle is one subjected to plural times of surface-treatment and the last surface-treatment is carried out by a reactive organic silicon compound.
6. The electrophotographic photoreceptor described in the foregoing 5 in which the reactive organic silicon compound is methylhydrogenpolysiloxane.
7. The electrophotographic photoreceptor described in the foregoing 5 in which the reactive organic silicon compound is an organic silicon compound represented by Formula 1.
Rxe2x80x94Sixe2x80x94(X)3xe2x80x83xe2x80x83Formula 1
In the formula R is an alkyl or aryl group, X is a methoxy or ethoxy group or a halogen atom.
8. The electrophotographic photoreceptor described in the foregoing 7 in which R in Formula 1 is an alkyl group having from 4 to 8 carbon atoms.
9. The electrophotographic photoreceptor described in any one of the foregoing 5 to 8 in which at least one of the plural surface-treatments is carried out by one or more compounds selected from the group consisting of alumina, silica and zirconia.
10. The electrophotographic photoreceptor described in any one of the foregoing 4 to 9 in which the titanium oxide particle is surface treated by both or one of silica and alumina and then surface treated by the reactive organic silicon compound.
11. The electrophotographic photoreceptor described in the foregoing 4 in which the titanium oxide particle is surface-treated by an organic silicon compound having a fluorine atom.
12. The electrophotographic photoreceptor described in any one of the foregoing 1 to 11 in which the interlayer contains polyamide resin.
13. An image forming apparatus for repeatedly forming images comprising an electrophotographic photoreceptor and, arranged around them, a charge providing member, a light-exposing member and a developing member in which the electrophotographic photoreceptor is the electrophotographic photoreceptor described in any one of the foregoing 1 to 12.
14. A processing cartridge to be used in an image forming apparatus for repeatedly forming images comprising an electrophotographic photoreceptor and, arranged around them, a charge providing member, a light-exposing member, a developing member, a transferring member and a cleaning member, in which the electrophotographic photoreceptor has the electrophotographic photoreceptor described in any one of the foregoing 1 to 12, and at least one of the charge providing member, the light-exposing member, the developing member, transferring member and the cleaning member is made into an unit and is constituted so as to be able to get and off to an image forming apparatus.